Jan Vroonhof writes:
I really think you want to change window height to take the gutter
into account. window-height is really meant to do as good an
approximation of window-displayed-height without doing a redisplay.
The main purpose is to make code from the pre-varying-height-font era
(i.e. FSF code) work correctly.
I agree. The gutter is a frame element. Only per window
elements like scrollbars and modelines should steal space from
window-height. The gutter should steal space from the frame
before the remaining space is allocated for the windows.